An ink jet recording method is a printing method in which droplets of an ink composition are allowed to fly and deposited on a recording medium such as paper to perform printing. This ink jet recording method is characterized by that images having high resolution and high quality can be printed at high speed. The ink composition used in the ink jet recording method is generally one mainly comprising an aqueous solvent and containing a coloring component and a wetting agent such as glycerin for the purpose of preventing clogging.
Further, when printing is performed on a recording medium such as paper or cloth that is hard for the aqueous ink composition to penetrate thereinto, or a plate or a film made of a material such as metal or plastics into which the aqueous ink composition does not penetrate, for example, a resin such as a phenol, melamine, vinyl chloride, acrylic or polycarbonate resin, the ink composition is required to contain a component which can allow the coloring material to be stably fixed to the recording medium. In particular, when printing is performed on a printed-circuit board or the like, the ink composition is required to have quick drying properties and solvent resistance.
To such a demand, there has hitherto been proposed an ink composition comprising a component polymerizable by ultraviolet irradiation (for example, see patent document 1). Further, an ultraviolet curing type ink composition comprising a coloring material, an ultraviolet curing agent, a photopolymerization initiator and the like has been proposed (for example, see patent document 2). According to these ink compositions and ink jet recording methods, it is disclosed that blurring of the ink composition on the recording medium can be prevented to improve image quality.
In the ink jet recording method using the ink composition comprising the component polymerizable by ultraviolet irradiation as described above, an ultraviolet lay is irradiated after the ink composition has been deposited on the recording medium. Thereupon, the photopolymerization initiator in the ink composition forms radicals, thereby initiating polymerization of an oligomer and a monomer to cause curing. Accordingly, the coloring material in the ink composition is firmly fixed onto the recording medium. It is considered that printing which is high in film strength, solvent resistance and color density and decreased in blurring and unevenness can be realized by this firm fixing.
However, the ultraviolet curing type ink composition comprising the coloring material, the ultraviolet curing agent, the photopolymerization initiator and the like as described above has insufficient wettability to a surface of a nonabsorbable material such as glass or metal, so that repellency occurs on a print surface and at an interface at the time when recoating has been performed, resulting in failure to obtain a clear color image.
There is disclosed an ink composition in which a polyether-modified silicone oil is allowed to be contained as a surface tension regulator in an ultraviolet curing type ink composition for the purpose of improving wettability to a surface of a nonabsorbable material (for example, see patent document 3). However, the polyether-modified silicone oil improves wettability to only a surface of a specific nonabsorbable material, so that it is unsatisfactory.
Patent Document 1: JP-A-3-216379
Patent Document 2: U.S. Pat. No. 5,623,001
Patent Document 1: JP-A-2003-147233